Air circulating means



A. E. KLINE ET AL 2,852,181

AIR CIRCULATING MEANS Sept. 16, 1958 2 Sheets-Sheet 1 Filed May 7, 1956 FIG.

.ul 42 l FIG. 2.

JNVI'L'VTORS ARTHUR E KHNE By WENDELL H WEBSTER ATTORNEY Sept. 16, 1958 A. E. KLINE ET AL AIR CIRCULATING MEANS 2 Sheets-Sheet 2 Filed May '7, 1956 INVENETORS ARTHUR E. K

STER

WENDELL H BY ATTORNEY United States Patent M AIR CRCULATING MEANS Arthur E. Kline and W endell H. Webster, Albion, Mich., assignors to McGraw-Edison Company, a corporation of Delaware Application May 7, 1956, Serial No. 582,967

1 Claim. (Cl. 230119) This invention relates to air circulating means for particular, but not exclusive, use in room air conditioners.

The invention involves a novel centrifugal fan design, for use in conjunction with a booster fan of the propeller type, the novel features residing in the fans themselves and in the adaptation of the fan combination to circulating apparatus such as a room air conditioner.

It is an object of this invention to enhance design flexibility by providing means for increasing the volume of air circulated through an appliance such as that mentioned without sacrificing the low noise level indispensable to its residential application.

A further object is to provide a one-piece centrifugal fan especially designed for die casting and further adapted to accommodate the attachment of an auxiliary or booster fan, preferably of the one-piece propeller type. An incident to this object being greater economy resulting from permitting use of a certain centrifugal fan by itself where a predetermined volume of air must be moved and using the same centrifugal fan with a single-piece auxiliary booster fan when it is desired to augment the air flow in the same or a larger capacity appliance.

More general objects are to provide a fan assembly which is versatile, efficient, simple in form, easy to balance, compact and economical to manufacture. Other specific objects will appear periodically throughout the ensuing specification.

By way of example, the novel air circulating means is illustrated in conjunction with a room air conditioner, although it is by no means intended to establish a limitation upon its versatility.

The invention will be more clearly understood by reference to the following drawing in which:

Fig. l is a horizontal, sectional, plan view of a room air conditioner embodying the novel air propelling means constituting the invention;

Fig. 2 is a front elevational view of the apparatus illustrated in Fig. 1, partly in section;

Fig. 3 is an exploded isometric View of the new centrifugal fan and booster fan assembly; and,

Fig. 4 is a fragmentary detailed view of means for attaching the booster fan to the centrifugal fan.

Referring to Fig. 1, it will be seen that the combination or assembly comprising the centrifugal fan 1 and a propeller type booster fan 2 is installed in the interior sheet metal casing 3 of a room air conditioner for the purpose of illustrating the path of the air flow which the fan assembly is intended to effect. For the sake of avoiding the immaterial, the exterior decorative housing of the air conditioner is omitted.

The conditioner used for illustrating an application of the novel fan assembly may be a conventional type including usual components such as a refrigeration compressor 4, a condenser coil 5 and an evaporator or cooling coil 6. Condenser coil 5 is provided with a sheet metal conical shroud 7 for directing air, which is delivered by a condenser fan 8 through coil 5 whereupon it is expelled Patented Sept. 16, 1958 into the outside atmosphere. Condenser fan 8 is not included as being part of the inventive subject matter covered by this disclosure.

There may be one or more screened openings 9 in casing 3 for the purpose of assuring a reliable supply of cooling air to the condenser coil 5. Metallic casing 3 is partitioned by a number of different vertical sheet metal walls such as 14 and 15 for a purpose which will be explained later. It is to be understood that casing 3 would, in practice, be enclosed, but the cover is omitted in the illustration.

Condenser fan 8 and the combination of centrifugal fan 1 and auxiliary booster fan 2 are driven on remote ends of a common shaft 16 of a relatively low speed electric motor 17 located approximately centrally within casing 3. The back of fan 1 is enclosed by a wall 15 which is impervious except where motor shaft 16 projects closely through it for supporting centrifugal fan 1.

The arrangement of the parts is such that the air circulated by the combined fan assembly is first drawn through a conventional, replaceable air filter 18, which stands vertically in front of the evaporator coil 6. There is a round intake opening 19 for the booster fan assembly perforated through a transverse vertical partition wall 20. Air circulated by centrifugal fan 1 is drawn through filter 18 and intake hole 19 and is centrifugally impelled upwardly and out forwardly through a room discharge opening 21 in a flow direction opposite from that of the air intake and in a horizontal plane lying above the flow plane of the incoming air. Intake hole 19 may be encompassed by a shroud ring 12 which aids in directing air through auxiliary fan 2 into the intake side of centrifugal fan 1. Vertical partition wall 15, behind fan 1, complements transverse partition wall 20, ahead of the propeller fan 2 for jointly creating, in conjunction with inclined wall 13, the well known scroll chamber configuration in which centrifugal fans are generally housed.

The means for controlling air flow through the air conditioner casing 3 are conventional in the respect that they include means for admitting outside fresh air into the room, exhausting stale air from the room through the condenser fan, and for admitting additional fresh air through the condenser fan. This is achieved by an appropriately located rotary damper designated generally bythe reference numeral 22 and arranged to close at one time any of three openings 23, 24, or 25. The damper .22 shown is simple in form and comprises horizontal upper -30 and lower 31 disks of plastic or other material joined by an integral, longitudinal, arcuate, vertical segment 32 rotatable with the disks. Rotation of damper 22 to its various positions is accomplished by turning a control knob 33 attached to the upper disk 30 as shown.

In Fig. 1, segment 32 is positioned to close opening 25. This places openings 23 and 24 in communication so that fresh air may be drawn through rear fresh air inlet 34 and discharged through the condenser co-il under the influence of condenser fan 8. Since the front of the air conditioner extends into the room it will be apparent that when segment 32 is in a position corresponding with Fig. l, the only air handled by the fan assembly 1, 2 will be room air recirculated by drawing it through filter 18 and discharging it through the room discharge outlet 21. The channeling of air flow when the damper segment 32 is in either of the other of its two positions where it closes openings 23 or 24 will be obvious upon cursory examination and will not be explained in greater detail because of it not having a direct bearing upon the specific invention here involved.

Attention is now invited to Fig. 3 in conjunction with which a more detailed explanation of the novel fan structure will be set forth. For the sake of clarity, the booster .fan 2 is shown detached from and displaced along:the

isometric axis of the novel centrifugal fan 1. The details of centrifugal fan 1 will be described first.

Centrifugal fan 1 is a forward pitched, multi-blade, one-piece die cast fan. Its metal content is preferably zinc although it may be cast as easily of aluminum. Fan 1 comprises a spider made up of a plurality of thin, flat spokes 36 each provided with a reinforcing rib 37 which is joined with a central hub 38 having a bore 3 for mounting on the shaft 16 of fan motor 17. Spokes 36 extend radially from the hub where they unite with a flat blade carrying annulus 40. A solid flat disk may be substituted for the spokes 36 and annulus 40 and the term annulus is here intended to imply either alternative. Although it is somewhat obscured in the drawing, the backs of spokes 36 lie in the same plane as the back of annulus 40. Consequently, the back of the novel fan 1 is smooth and coplanar.

The centrifugal fan 1 is provided with a multiplicity of axially extending concave blades 41 inclined in the direction of rotation of the fan, that is, counterclockwise when viewed in the example of Fig. 3. Of course, fan 1 vmay be run clockwise as shown, or in the alternative,

blades 41 may be inclined oppositely for clockwise rotation. Blades 41 each have a leading edge 42 and a trailing edge 43, the leading edge being the air output edge and the trailing edge being on the air intake side of the fan. The various blades 41 are cast integrally with and project perpendicularly from flat annular ring 40. For the purpose of facilitating die casting, leading edges 42 are flush with the outside diameter of annular ring 40 about the entire periphery of the fan. Blades 41 may be flat and inclined in either circumferential direction and still come within the basic inventive concepts of this disclosure.

The chosen width of fan blades 41 is dependent upon a number of design considerations among which are: the

I air displacement desired and the tolerable noise level. It

band. In prior art fans of the stamped type, the number of blades can be increased only at the expense of their width. Whereas, if the blades are of the insert type, the latter disadvantage is overcome, but at the expense of increased complexity and cost.

At the open end of the fan, constituting the inlet side, the blades are tied in, by a die cast Web 44 near their leading edges to a peripheral blade supporting bead ring 45. Bead ring 45 may have any cross section such as round, square, triangular or rectangular, but it is preferable that it have a semi-circular front periphery, straight sides and a comparatively flat rear periphery according to details which may be seen in Fig. 4.

The overall outside diameter of bead ring 45 is not limited to any specific dimension, but the inside diameter thereof should preferably be larger than the outside diameter of the blade carrying annular flat ring 40 on the spider end of the fan to facilitate die casting. This construction enables firmly tying in the leading edge 42 of blades 41 to the inner periphery of head ring 45 by means of the small webs of metal 44 which are formed during the single operation die casting process. Web 44 is rather small in section but is nevertheless suflicient to impart rigidity to blades 41 and to assure that their spacing is maintained. Since the blades are die cast integrally with annular ring 40 they are supported in cantilever adequately to resist forces of deformation due to impacting air being delivered by the fan.

The purpose of making the diameter of bead ring 45 'larger than the outer diameter of either the blades 41 or zannular ring 40 will be eminently clear when the die casting operation is considered. There are, of course, two die sections needed to form the centrifugal fan 1 in a conventional die casting machine, not shown. Because of the centrifugal fans complexity and its difierent elements being disposed in different directions, it is necessary that the parting of the die sections occur on what might be termed the equator lying along the mid section of head ring 45. The line of parting is indicated by points designated 46 which may be joined by a straight line on head ring 45, see Fig. 4.

Insofar as is known, no one practicing the art of fan manufacture has heretofore successfully designed a fan which lends itself to being easily die cast. From experience with the instant fan design, it is known that the die cast fan can be produced more economically than pressed steel fans which are currently available. Moreover, as implied above, the centrifugal fan has the additional advantage of being a one-piece construction which may be mass produced with consistent accuracy and furthermore permits attainment of optimum fan characteristics by reason of allowing the blades to be cast in any width and number desired.

Static balancing of centrifugal fan 1 is very simple and only entails cutting 01f a tip or some other portion of a blade 40 on the heavy side of the fan, as indicated by the dashed line 47 in Fig. 3. Thus the fan is characterized by its ease of production and balancing; and it is therefore, an ideal design for use in mass produced appliances where small cost reductions quickly accumulate large savings.

In Fig. 1 it will be noted that centrifugal fan 1 has attached .to it a propeller type auxiliary booster fan 2. In Fig. 3, booster fan 2 is located concentric with, but axially displaced from, centrifugal fan 1 for the purpose of avoiding superposition of lines and facilitating its description. Turning attention to propeller fan 2 we note that it is a single-piece stamped construction including a plurality of blades 50 whose leading edge 51 lies on one side of a plane defined by a thin flange ring 52 joined to the blades by a deformed web of metal 53. The trailing edges 54 of booster fan 2 lie on the opposite side of the plane defined by flange ring 52 and the blades are tied together centrally by means of an intersecting ribbed hub 55, which latter has no rotational bearing, nor is one necessary, because propeller fan 2 is carried by centrifugal fan 1. Fan 2 is formed in a single-piece of aluminum or other thin sheet metal. When the booster arrangement is employed, fans 1 and 2 are connected serially for continuously impelling a common volume of In this illustration of the invention, outer margin of flange ring 52 on fan 2 is provided with an annular groove 58 of substantially semi-circular cross section which complements and registers with the curvature of head ring 45 when fans 1 and 2 are placed concentrically against each other. The details of the method for fastening booster fan 2 onto centrifugal fan 1 are clearly evident in Fig. 4 which shows the annular groove 58 in bearing relation upon the bead ring 45 and held in that position by a substantially U-shaped metallic spring clip 59 which embraces flange 52 and the beadring 45 of centrifugal fan 2 in the manner shown. For relatively low speed fans ordinarily found in home appliances, four such snap rings are adequate for holding the booster propeller fan 2 on the centrifugal fan 1. Furthermore, the rotational 'speed of forward pitched fans is usually so low as to the air displacement requirements are greater, all without undertaking extensive changes in design of the air conditioner unit.

It has been found in practice that, by attaching the booster fan 2, the air volume output of the appliance may be increased at least 25%, holding motor speed constant, without perceptibly increasing the noise level of the fan assembly. It has been further discovered that the overall efliciency of the combined centrifugal fan 1 and propeller fan 2 assembly is actually increased so that the increased electrical power required to drive the fans is not as great as might be expected in accordance with the increased air output. This is partly true, perhaps, because the booster fan 2 builds up the pressure on the interior of the centrifugal fan 1 and overcomes the effect of the inherent difference in peripheral velocity of the leading and trailing edges of the blade due to the difference in the radius generated from their common center of rotation. Moreover, it is known that the efficiency of a propeller type fan increases as the static pressure against which it operates decreases. Combining the booster fan 2 with the centrifugal fan 1 enhances this phenomena, for although the booster tends to increase the static pressure interiorly of the centrifugal fan, the booster nevertheless operates against a relatively loW static pressure head because of the inherent tendency of a centrifugal fan to develop a much lower static pressure in the circular interior volumetric space defined by the trailing deges 43 of its blades.

The characteristics of the centrifugal fan by itself and in combination with the booster fan are believed unique; and the same may be said of their adaptation to a room air conditioner.

Although the invention has been described with respect to a centrifugal fan having forward pitched blades, those versed in the art will understand how the disclosure hereof may be readily adapted to a comparable fan having straight or backward pitched blades. Moreover, the same artisans will understand that the propeller fan may take a variety of forms. Accordingly, although only a preferred embodiment of the invention has been described it will be understood that the invention may be variousl embodied and is to be interg-"eted as claimed.

It is claimed: in a room air conditioner comprising a fan chamber having inlet and outlet openings through which air subjected to cooling may be circulated, a one-piece die-cast centrifugal fan in said chamber having its air inlet side presented to said inlet opening, said centrifugal fan including a blade carrying annulus remote from the fan inlet side and a plurality of blades die-cast with and projecting perpendicularly from the annulus, said fan blades having leading and trailing edges lying wholly within a circle encompassed by the outer margin of the annulus,

a bead ring interconnecting said blades at their ends remote from the annulus, the inside margin of the bead ring lying wholly radially outside the various leading edges of the blades, a die-cast web conjoining each leading edge to the bead ring in a region spaced from the axially extreme face of the bead ring to thereby recess the blade ends with respect to the ring face, a detachable auxiliary propeller fan including plural blades projecting away from the inlet side of the centrifugal fan and pitched to force air therein, a flange ring interconnecting said propeller blades and including an annular groove adapted to complementarily register with the bead ring and thereby admit a portion of the flange ring into the recess defined by the blade ends, and spring clop means jointly embracing the flange ring and bead ring for holding the auxiliary fan to the centrifugal fan.

References Cited in the file of this patent UNITED STATES PATENTS 902,533 Hubbard Oct. 27, 1908 997,678 Jalonick July 11, 1911 1,184,992 Pritchard May 30, 1916 1,513,763 Rowe Nov. 4, 1924 2,104,233 Leinweber Jan. 4, 1938 2,652,190 Meltzer et al Sept. 15, 1953 

